In the related arts, a control method based on temperature and a period is mainly used for defrosting an air conditioner. That is, under a heating mode, if tube temperature of an outdoor heat exchanger is lower than a specific value while satisfying a period condition, the air conditioner is controlled to enter a defrosting mode. If the tube temperature of the outdoor heat exchanger increases to another specific value while satisfying another period condition, the air conditioner is controlled to exit from the defrosting mode and to start the heating mode again.
The control method may defrost outside surfaces of the outdoor heat exchanger. However, for a case that there is a protecting housing surrounding the outdoor heat exchanger, the control method may have some troubles. For example, as a separation distance between the protecting housing and the outdoor heat exchanger is improper or as there is an installation error, frosting extends to the protecting housing from the outdoor heat exchanger such that defrosting is incompletely.